Liquid phase alkylation of aromatic hydrocarbons



United States Patent 3,238,267 LIQUID PHASE ALKYLATION 0F AROMATIC HYDROCARBONS Stephen M. Kovach, Highland, 1nd,, assignor to Sinclair Research, Inc., Wilmington, Del., a corporation of Delaware No Drawing. Filed Dec. 11, 1962, Ser. No. 243,738

7 Claims. (Cl. 260-671) This invention relates to a process for the selective alkylation of aromatics with olefins and is particularly concerned with the alkylation of aromatics with non-tertiary monoolefins containing 3 to 12, preferably 3 to 7, carbon atoms over a defined alkylation catalyst.

Alkylated aromatics are of value in many fields and some are particularly desirable as constituents of high octane aviation fuels and as sources of synthetic detergents. Although catalytic processes for the alkylation of aromatics have been suggested, aromatics alkylated with olefins under typical commercial conditions (vapor phase) over Friedel-Crafts type catalyst, e.g. AlCl have a high catalyst consumption due to the formation of a catalyst oil sludge layer and in addition require special equipment to combat their corrosive nature. The solid oxide type catalyst, e.g. silica-alumina, phosphoric acid on kieselguhr, etc., gives high conversion in olefin-aromatic alkylations but loses activity due to the laydown of carbonaceous material on the catalyst. This requires frequent high temperature regeneration and some catalyst systems are non-regenerable. The present process provides good utilization of the olefin as an alkylating agent to give excellent yield of alkylate from aromatics and olefins and the catalyst is resistant to deactivation by aromatic-complex formation or carbon laydown on the catalyst.

A process has now been discovered whereby C to C aliphatic, non-tertiary monoolefin hydrocarbons are alkylated with an aromatic over a select catalyst containing fluorine and alumina while employing a particular set of operating conditions. The olefins are primary and secondary monoolefins and may be straight or branched chain with the straight chain primary olefins being preferred. To obtain the desired results, it is important that the conditions of temperature and pressure employed in the process be such that the olefin remains essentially in the liquid phase. This necessitates maintaining processing temperatures below the critical temperature of the olefin, for instance when the olefin is propylene a temperature of below about 198 F., and operating pressures above the vapor pressure of the olefin at the processing temperature under essentially anhydrous conditions. In the alkylation convenient reaction temperatures are below about 200 F., for instance about 0 to 197 F. for propylene, preferably about 70 to 180 F., and the pressure often ranges from about 0 to 2000 p.s.i.g., preferably about 200 to 800 p.s.i.g. Space velocities in the range of about 0.1 to 20 LHSV (liquid hourly space velocity) have been found suitable but a space velocity of about 0.1 to LHSV is preferred. Under the select conditions employed tertiary olefins do not undergo aromatic alkylation, but instead polymerization; whereas the olefins yielding primary and secondary carbonium ions undergo aromatic alkylation with the present catalyst system. It is preferred that the aromatic hydrocarbon be present in excess of the stoichiometric amount necessary to achieve mono-alkylation; however, if poly-alkylation is desired, an excess of the olefin should be present in the reaction zone.

The aromatics, e.g. alkylatable aromatic hydrocarbons, suitable for alkylation in the present process include monoand polycyclic aromatic compounds such as ben- "ice zene and its lower alkyl homologues, e.g. toluene, the xylenes, etc., as well as analogous polynuclear derivatives such as naphthalene and indane, which may be substituted or unsubstituted. The substituted aromatic compounds are preferably methyl substituted. These compounds may correspond to the general formula:

(jar-R where R is an alkyl, including cyclo alkyl, radical containing generally from about 1 to 20, preferably from about 1 to 8 carbon atoms and where n is 0 to 3, R need not be the same alkyl group; R is an aromatic hydrocarbon ring, preferably C H f indicates a fused ring relationship (two carbon atoms common to two aromatic nuclei e.g. as in naphthalene); and m is generally 0 to 1 or more. The preferred aromatics, however, include benzene and alkyl benzenes corresponding to the above formula when m is 0. Benzene and toluene may be present in the feed material but for economic reasons, they are usually excluded from the feed. Suitable aromatic hydrocarbons include ortho-xylene, meta-xylene, paraxylene, ortho-ethyltoluene, meta-ethyltoluene, para-ethyltoluene, 1,2,3-trimethyl benzene, 1,2,4-trimethyl benzene, 1,3,5-trimethyl benzene or mesitylene.

Due to the exothermicity of the reaction and the narrow temperature operating range, it is preferred to employ internal means as heat sinks. This can be accomplished for instance by employing high aromatic to olefin ratios, inert hydrocarbon and catalyst diluents. The catalyst diluents are solid and the hydrocarbon diluents are liquid at the reaction conditions. The hydrocarbon diluent can be any hydrocarbon, unable to undergo polymerization, condensation, alkylation or other reaction under the process conditions. This would encompass paraffins, naphthenes, etc. The hydrocarbon diluent reduces the concentration of olefin in the liquid phase and at the catalyst surface and often acts as a heat sink. If aromatics are used as a diluent, benzene, toluene, xylene and other monoand (di-substituted) aromatics are undesirable since they may undergo alkylation with the olefin under the reaction conditions. The aromatic solvent should be non-alkylatable under the conditions utilized, i.e. they should be highly substituted as for instance tetra or higher substituted benzenes. The choice of solvent will depend on factors such as the olefin feed, etc., which tend to maximize alkylation and minimize polymerization. Suitable inert catalyst diluents are any materials not supporting the alkylation, e.g. tabular alumina, or which would destroy the alkylation activity of the catalyst. The amount of liquid diluent may be present in the range of about 0 to 10 or more, preferably about 0.5 to 2, volumes of diluent to about 1 volume of the olefin. The solid diluent may be present in a volume ratio of about 0 to about 10, preferably about 1 to 3, volumes of the solid diluent to about 1 volume of the catalyst. In addition, external sources of cooling may be utilized such as circulating cold water, co-ld feed, air, etc.

The catalyst of the present invention is an alumina base catalyst containing fluorine. The fluorine can be present in the catalyst in the form of the ion per se and in combination such as a metal fluoride, e.g. zinc or aluminum fluoride, fluosilicic acid, or fluoborate. The fluorine promoter is present on the alumina support in catalytically effective amounts. Generally this amount will fall within the range of about 1 to 20% by weight, preferably about 3 to 15% by weight. The catalyst support of the present invention is an activated or gamma family alumina, e.g. gamma, eta, etc., such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures. The catalyst base most advantageous is derived from a mixture predominating, for instance in about 65 to 95 weight percent, in one or more of the alumina trihydrates, i.e. bayerite I, randomite (norstrandite), or gibbsite, and also having about to 35 weight percent of alumina monohydrate (boehmite), amorphous hydrous alumina or their mixture. The alumina support can contain small amounts of other materials, e.g. solid oxides such as silica, magnesia, activated clays, titania, zirconia, etc. or their mixtures.

The catalysts can be prepared by impregnation using a water-soluble compound of the catalytic component or by precipitation methods well known to the art. The fluorine can be added to the catalyst base in any stage of its preparation; for instance, before or after it has been formed by tabletting or extrusion and calcined. After fluorine addition the catalyst can be calcined. In the case of fluoride alumina, the fluorine is commonly added through the use of a water-soluble fluoride compound. Although ammonium fluoride is generally preferred other water-soluble fluoride compounds, for example, ammonium fluosilicate, ammonium fluoborate, hydrofiuosilicic acid, hydrofluoric acid and the like can be employed.

To further illustrate the process of the present invention, Example I is included.

EXAMPLE I Meta-xylene and toluene were processed over a zinc fluoride on alumina catalyst in the presence of isobutylene and propylene, respectively. These runs were performed at room temperature and in the liquid phase. The specific conditions employed and the results obtained are shown in Table I below.

When meta-xylene was processed over the zinc fluoridealumina catalyst under liquid phase conditions in the presence of isobutylene the major product was polymer (dimer, trimer) and only a trace of alkylate was obtained. These results show that olefins yielding primary and secondary carbonium ions can undergo aromatic alkylation over the catalyst described in the invention at room temperature under liquid phase conditions, whereas olefins yielding tertiary carbonium ions undergo polymerization with little or no aromatic alkylation. i i

The catalyst of the present invention possesses unique fouling and regenerating features. By operating at low temperatures these catalysts become deactivated not by carbon laydown on the catalyst but lose activity by the plugging of the catalyst pores by heavy polymeric material. Alkylation activity can be restored by washing the catalyst with a suitable paraffin or aromatic hydrocarbon solvent as for instance, n-pentene or benzene. If solvent washing fails, reactivation can be brought about by heat treating the catalyst to 400 to 700 F. and purging with an inert gas such as nitrogen. This high temperature purge drives the heavy polymeric material out of the pores of the catalyst depositing only a small amount of carbon on the catalyst without loss in alkylation activity.

It is claimed:

1. A process for the selective alkylation of an alkylatable aromatic hydrocarbon having the formula:

where R is an alkyl radical containing from about 1 to carbon atoms; n is 0 to 3; R is an aromatic hydrocarbon ring; f indicates a fused ring relationship; and m is 0 to 1, with a C to C non-tertiary monoolefin hydrocarbon which consists essentially of contacting said aromatic hydrocarbon with said olefin in the liquid phase at a temperature below about 200 F., in contact with an alkylation catalyst consisting essentially of a catalytic amount of zinc fluoride supported on alumina.

2. The process of claim 1 wherein the temperature is about to F. and the pressure is about 200 to 800 p.s.i.g. and the olefin is propylene.

3. The method of claim 2 wherein the amount of zinc fluoride on the alumina support is about 3 to 15% by weight.

4. The method of claim 1 wherein a narrow temperature operating range is insured by employing an aromaticto-olefin ratio of at least 2 moles of alkylatable aromatic hydrocarbon to 1 mole of non-tertiary monoolefin, a nonalkylatable aromatic liquid diluent in a ratio of about 0.5 to 2 volumes of diluent to about one volume of the olefin and a catalyst diluent in a ratio of about 1 to 3 volumes diluent to 1 volume of catalyst.

5. The method of claim 4 wherein the catalyst diluent is tabular alumina.

6. The process of claim 1 wherein R is an alkyl radical containing from about 1 to 8 carbon atoms.

'7. The process of claim 2 wherein the aromatic hydrocarbon is toluene.

References Cited by the Examiner UNITED STATES PATENTS 2,584,103 2/1952 Pines et al. 260671 DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner. 

1. A PROCESS FOR THE SELECTIVE ALKYLATION OF AN ALKYLATABLE AROMATIC HYDROCARBON HAVING THE FORMULA: 